1. Field of Invention
The present invention relates generally to a liquid oxygen delivery system, and, more particularly, to a liquid oxygen delivery system that includes a portable recharger for providing supplemental liquid oxygen to a portable liquid oxygen delivery device for increasing the utilization capacity of the portable liquid oxygen delivery device.
2. Description of the Background Art
The delivery of supplemental oxygen to a patient is typically prescribed for individuals suffering from pulmonary/respiratory problems. The prescription and delivery of supplemental oxygen is undertaken to ensure that sufficient oxygen levels are received by the patient. Situations where supplemental oxygen may be prescribed include individuals afflicted with a chronic obstructive pulmonary disease, such as asthma, as well as individuals suffering from diseased or damaged lungs.
The delivery of supplemental oxygen may be provided utilizing one of three predominant methods. For non-ambulatory patients, or for use during the non-ambulatory period of an individual, oxygen may be provided from a stationary oxygen concentrator that generates oxygen from air, typically using a pressure swing absorption gas separation system. While suitable for their intended purpose, oxygen concentrators are generally ill-suited for portability due the relatively bulky and heavy gas compressor and sieve beds needed to generate a practical quantity of oxygen, and, therefore, are not intended for use with an ambulatory individual.
A second predominant oxygen delivery method is a compressed oxygen system in which the oxygen to be consumed by the user is compressed and stored in a high pressure storage vessel or tank. These storage vessels can be made small enough so as to be portable. Compressed gas storage systems are generally prescribed when the user does not need oxygen all the time, such as only when walking or performing physical activity. One disadvantage of compressed oxygen systems is that oxygen stored under pressure may create a hazard if the storage vessel is damaged, which can occur if it is dropped, bumped, punctured, etc. Also, small, portable oxygen tanks hold a relatively small amount of gas. Thus, they are limited in how long the oxygen inside the tank will last, which will depend on the prescribed flow rate and the type/size of the tank.
A third predominant oxygen delivery method, which is typically used as an alternative to compressed oxygen systems, is a liquid oxygen (“LOX”) system. A conventional LOX system includes a large stationary LOX storage canister that is located at and remains at the user's home. The stationary LOX canister is replenished periodically from a mobile LOX storage vessels, which is typically a truck carrying a large quantity of LOX. The LOX system also includes a small, portable delivery apparatus weighing from five to thirteen pounds that can be filled from the stationary unit for trips outside the home. The portable delivery apparatus converts the liquid oxygen to a breathable gas for consumption by the user. These systems have limited utilization due to the low LOX capacity of the portable delivery apparatus and the administered LOX flow rate. Furthermore, even when not in use, the LOX within the portable delivery apparatus evaporates at a typical rate of one pound per day, emptying the portable delivery apparatus LOX supply over time even if it is not used. Consequently, a disadvantage of a portable LOX system includes the requirement that the user must return home regularly, such as by the end of the day, to refill the portable delivery apparatus from the home stationary LOX storing canister.
One such LOX system is disclosed in U.S. Pat. No. 6,742,517 (“the '517 patent”) entitled, High Efficiency Liquid Oxygen Storage and Delivery System. As disclosed in this patent, a typical LOX system includes a stationary LOX storage canister located in an individual's home and a portable LOX delivery unit that the patient uses outside the home. The stationary LOX storage canister must be periodically refilled with LOX by a distributor via a truck, van, or other vehicle capable of carrying a large quantity of liquid oxygen. The name of the portable delivery unit in the commercial implementation of this LOX system and described in the '517 patent is the HELiOS®. As identified at the HELiOS website, www.heliosoxygen.com, the HELiOS H300 portable LOX delivery unit has a limited capacity for storing liquid oxygen. This capacity is limited to eight to ten hours of usage, after which the LOX is depleted.
The HELiOS weighs approximately 3.6 pounds when completely filled with LOX, and approximately 2.75 pounds empty. The HELiOS portable unit is designed to be refilled from a stationary LOX storage canister and has a LOX capacity of 0.9 pounds. Because the typical evaporation of LOX is one pound per day, the LOX within the HELiOS unit will most likely evaporate during a day, even without the LOX being utilized by an individual. Furthermore, the evaporation of LOX can occur at a faster rate than one pound per day when the LOX canister is actually being worn by an ambulatory patient, because the movement of the patient increases the friction within the LOX canister, thus elevating the temperature of the LOX and expediting the evaporation of the LOX.
While portable LOX systems are suitable for their intended purposes, they nonetheless have a significant drawback, namely their limited LOX capacity. Current portable LOX systems provide an individual with only a short time of LOX availability. Hence, the ambulatory patient is, in effect, tethered to their home because they must remain within close proximity of the home in order to have access to their LOX supply for refilling the portable LOX system. As noted with respect to the HELiOS, it only has a capacity of eight to ten hours, which is not typically sufficient for a fairly active individual who also works.
One solution to extend the time away from home by an ambulatory LOX patient consists of incorporating a standard stationary (home) LOX storage unit into an automobile for subsequent refilling of the portable LOX device. This solution requires retrofitting an automobile to accommodate the large liquid oxygen tank. Such LOX tanks are very large, bulky, and extremely heavy, weighing over a hundred and ten pounds. Such arcane measures of retrofitting an automobile are expensive, and typically require a large automobile such as a truck or SUV. Thus, retrofitting is not practical for most individuals and also limits the overall mobility of an individual, as they must ensure that they are either located close to home or near their respective retrofitted automobile.
For those individuals who have not retrofitted their vehicle, traveling even small distances is a problem. For instance, because the provision of liquid oxygen for therapeutic purposes requires a prescription, the refilling of a portable device cannot typically be done if travel occurs across state lines. Hence, a problem arises for people utilizing prescription oxygen when they travel among states. They must consider how long they can travel between portable refills, and how can the refill be accomplished.